For example, as a compressor for compressing refrigerant, which is built into a vapor compression type refrigerator built into an automotive air conditioning apparatus, conventionally several types of mechanism are known. For example, Japanese Unexamined Patent Publication No. H 11-280644 discloses a swash-plate type compressor which converts rotational motion of a rotation shaft into reciprocating motion of a piston using a swash-plate, and performs compression of refrigerant by this piston. FIG. 6 and FIG. 7 illustrate one example of such a conventionally known swash-plate type compressor.
A casing 2, constituting a compressor 1, is formed by sandwiching a central main body 3 between a head case 4 and a swash-plate case 5 from both sides in the axial direction (left-right direction in FIG. 6), and then joining these with a plurality of fastening bolts (not shown). On the inside of the head case 4, there is provided a low pressure chamber 6 and a high pressure chamber 7. Also, between the main body 3 and the head case 4, a tabular partition plate 8 is sandwiched. The low pressure chamber 6, which is shown in FIG. 6 as if divided into a plurality of sections, has the sections communicating with each other and connected to a single inlet port 9 (FIG. 7) provided on the outside surface of the head case 4. Furthermore, the high pressure chamber 7 is connected to an outlet port (not shown) also provided on the head case 4. Moreover, the inlet port 9 is connected to the outlet of an evaporator (not shown) constituting this vapor compression type refrigerator, and the outlet port is connected to the inlet of a condenser (not shown) constituting this vapor compression type refrigerator.
Within the casing 2, a rotation shaft 10 in a state of spanning between the main body 3 and the swash-plate case 5, is freely supported for rotation alone. That is to say, both ends of the rotation shaft 10 are supported by a pair of radial needle bearings 11a and 11b, on the main body 3 and the swash-plate case 5, and the thrust load exerted on this rotation shaft 10 is freely supported by a pair of thrust needle bearings 12a and 12b. Of the pair of thrust needle bearings 12a and 12b, one (right hand side in FIG. 6) thrust needle bearing 12a is provided between a part of the main body 3 and a step portion 13 formed on one end (right end in FIG. 6) of the rotation shaft 10, via a disc spring 14. Also, the other thrust needle bearing 12b is provided between a thrust plate 15 externally fitted to the outer circumferential surface of an intermediate part of the rotation shaft 10 and the swash-plate case 5.
Moreover, on the inside of the main body 3 constituting the casing 2 surrounding the rotation shaft 10, is formed a plurality (for example in the example shown on the figure, there are six evenly spaced in the circumferential direction) of cylindrical bores 16. Inside the plurality of cylindrical bores 16 formed in such a way on the main body 3, a sliding portion 18 provided at the tip half portion (right half of FIG. 6) of the respective pistons 17 is fitted to allow free displacement in the axial direction. Moreover, the space between the bottom face of the cylindrical bore 16 and the tip end surface of the piston 17 (right end surface in FIG. 6) serves as a compression chamber 19.
Furthermore, the space which exists on the inside of the swash-plate case 5 serves as a swash-plate chamber 20. On the outer circumferential surface of the intermediate part of the rotation shaft 10 located within this swash-plate chamber 20, a swash-plate 21 is fixed with a predetermined inclination angle with respect to the rotation shaft 10 such that this swash-plate rotates together with the rotation shaft 10. A plurality of locations in the circumferential direction of the swash-plate 21 and each of the pistons 17 are individually linked by means of a pair each of sliding shoes 22. Therefore, internal surfaces (mutually facing surfaces) of these individual sliding shoes 22 are made smooth faces, and are slidingly contacted with a part near the outer diameter on both side faces of the swash-plate 21 which are similarly smooth faces. On the other hand, on the base end portion of the respective portions 17 (the end portion farther from the partition plate 8; the left end portion in FIG. 6), is formed integral with each of the pistons 17, a connection portion 23 which together with the sliding shoes 22 and the swash-plate 21 constitutes a driving force transfer mechanism. Moreover, a holding portion 24 for holding the pair of sliding shoes 22 is formed on the respective connecting portions 17.
The outside end surface of each of the connecting portions 23, by means of a guide surface (not shown in the figure), is allowed free displacement only in the axial direction (left-right direction in FIG. 6) of the piston 17. Therefore, each of the pistons 17 is also fitted within the cylindrical bore 16 in such a way as to allow displacement only in the axial direction (rotation is not possible). As a result, each of the connecting portions 23 pushes and pulls each of the pistons 17 in the axial direction in accordance with the oscillating reciprocal displacement of the swash-plate 21 due to the rotation of the rotation shaft 10, and reciprocates each of the sliding portions 18 within the cylindrical bore 16 in the axial direction.
On the other hand, in the partition plate 8, which is sandwiched at the contact portion between the main body 3 and the head case 4, for partitioning the low pressure chamber 6, the high pressure chamber 7 and each of the cylindrical bores 16, is formed penetrating in the axial direction, an inlet 25 for communicating between the low pressure chamber and each cylindrical bore 16, and an outlet for communicating between the high pressure chamber 7 and each cylindrical bore 16. Also, in the part of each of the cylindrical bores 16 which faces one end of each of the inlets 25, is provided a reed valve type inlet valve 27, which allows only flow of refrigerant vapor from the low pressure chamber 6 to each of the cylindrical bores 16. Also, in the part of the high pressure chamber 7 which faces the opening on the other end (right side in FIG. 6) of the outlet 26, is provided a reed valve type outlet valve 28, which allows only flow of refrigerant vapor from the cylindrical bore 16 to the high pressure chamber 7. In this outlet valve 28, a stopper 29, which restricts displacement in the direction away from each of the outlet valve 26, is attached.
The rotation shaft 10 of the compressor 1 constructed in the above manner is driven by the propulsion engine of an automobile. Therefore, in the case of the example shown in the figure, on the periphery of a support member, in other words a support cylinder 30, provided at the center of the outside surface (left side surface in FIG. 6) of the swash-plate case 5 constituting the casing 2, is rotationally supported a driven pulley 31, by means of a double-row bearing. This driven pulley 31 is constructed in an overall annular form with a C-shaped cross section, and a solenoid 33, which is fixed to the outside surface of the swash-plate case 5, is provided within an internal cavity of the driven pulley 31.
On the other hand, at an end portion of the rotation shaft, which protrudes from the support cylinder 30, is fixed a mounting bracket 34, and around the circumferential surface of this mounting bracket 34, is supported an annular plate of magnetic material, via a plate spring 36. This annular plate 35, when there is no current through the solenoid 33, is separated from the driven pulley 31 due to the elasticity of the plate spring 36, as shown in FIG. 6. However, when there is a current through the solenoid 33, it is attracted towards this driven pulley 31, and hence allows the transmission of torque from this driven pulley 31 to the rotation shaft 10. That is to say, the solenoid 33, the annular plate 35 and the plate spring 36, constitute an electromagnetic clutch 37 for connecting and disconnecting the driven pulley 31 and the rotation shaft 10. Also, between the driving pulley fixed to the end of the crank shaft of the propulsion engine and the driven pulley 31, is spanned an endless belt 38. Furthermore, in a state where the driven pulley 31 and the rotation shaft 10 are connected by the electromagnetic clutch 37, the rotation shaft 10 is rotated based on the rotation of the endless belt 38.
The operation of the swash-plate type compressor 1 formed in the above manner is as follows. That is to say, in order to perform cooling and dehumidification of the automobile interior, in the case of operating a vapor compression type refrigerator, the rotation shaft 10 is rotated by the propulsion engine, being the driving source. As a result, the swash-plate 21 rotates, and the sliding portions 18 constituting the multiple pistons 17 reciprocate within the respective cylindrical bores 16. Furthermore, in accordance with such reciprocation of the sliding portions 18, the refrigerant vapor sucked in from the inlet port 9 is sucked from the low pressure chamber 6 through each inlet 25 into the compression chambers 19. This refrigerant vapor, after being compressed inside each of the compression chambers 19, is sent out to the high pressure chamber 7 via the outlets 26, and discharged from the outlet port.
The compressor shown in FIG. 6 is one in which the inclination angle of the swash-plate with respect to the rotation shaft is unchangeable, and hence the refrigerant discharge volume is fixed. On the other hand, a variable displacement swash-plate type compressor in which the inclination angle of the swash-plate with respect to the rotation shaft can be changed in order to change the discharge volume in accordance with cooling load and the like, is conventionally widely known from, for example, the disclosure of Japanese Unexamined Patent Publication No. H 8-326655 and so on, and is commonly implemented. Moreover, as a compressor for a vapor compression type refrigerator constituting an automobile air conditioning apparatus, the use of a scroll type compressor is also being researched in some places. Furthermore, in relation to a conventional compressor in which a piston is reciprocated by means of a ball joint, this is still also being used in some places.
Whichever the structure of the compressor used, the compressor constituting the automobile air conditioning apparatus is driven by the endless belt spanning between the driving pulley fixed to the end of the crank shaft of the propulsion engine and the driven pulley provided on the compressor side. Therefore, a radial load based on the tension force of the endless belt, is exerted on the bearing which rotatably supports the driven pulley. In order to perform reliable power transmission without slippage, between the endless belt and each of the pulleys, the tension force on the endless belt, in other words, the radial load, becomes correspondingly large. Therefore, as a bearing for supporting the driven pulley, in order to support this large radial load, it is necessary to use one with sufficient load capacity.
When the double row ball bearing 32 incorporated in the conventional structure shown in FIG. 6 is viewed from this perspective, the spacing D of balls 39 arranged in a double row is large, and hence the structure is said to be one which can ensure sufficient load capacity. However, with the double row ball bearing 32, the dimensions in the axial direction becomes bulky. On the other hand, recently, in consideration of the global environment, in an attempt to improve fuel efficiency of automobiles, miniaturization and lightening of automobile auxiliary equipment such as the compressor is demanded. Furthermore, a demand has also arisen for shortening of the axial dimensions of rolling bearings for supporting driven pulleys incorporated into automobile auxiliary equipment.
In response to such demands, as a rolling bearing for supporting the driven pulley, the use of single row deep groove ball bearings and three point or four point contact type ball bearings is being researched. However, with such ball bearings, rigidity with respect to the load, mainly the moment load, exerted on the driven pulley, cannot be easily ensured, and it is difficult to ensure a sufficient low-vibration property (propensity for not vibrating) or durability. That is to say, there are occasions where, though slight in magnitude, the moment load from the driven pulley acts on the rolling bearing. However, rigidity of the single row deep groove type ball bearing with respect to the moment load is low. Also, regarding the three point to four point contact type ball bearing, though rigidity with respect to the moment load is higher than the ordinary single row deep groove type ball bearing, there are occasions where the rigidity is not always sufficient due to the relationships such as the magnitude of the tension force on the endless belt or the arrangement (eccentricity between the direction of radial load and the location of the ball bearing center). As a result, vibration as well as noise during the operation becomes more likely, and it is difficult to ensure durability.
The pulley support double row ball bearing of the present invention was invented in consideration of such circumstances.